This application is the national phase under 35 U.S.C. xc2xa7371 of PCT International Application No. PCT/FR00/00276 which has an International filing date of Feb. 7, 2000, which designated the United States of America and was not published in English.
Surgery to correct ametropia using the technique of Prof. Barraquer in combination with an excimer laser is a surgical technique that is now widely developed and used on a large scale. It makes use of surgical instruments known as xe2x80x9cmicrokeratomesxe2x80x9d which essentially comprise a ring for fixing on the eye to be operated on so that the cornea projects into the center of the ring, and a moving cutting device guided relative to the fixing ring and comprising firstly a surface for flattening of the portion of the cornea that projects into the ring and secondly a generally-oscillating cutting blade whose cutting edge is situated immediately behind the flattening surface and at a determined distance therefrom measured vertically so as to define the thickness of the corneal lamella which is thus subjected to resection.
The present invention is a variant embodiment of known instruments for cutting the cornea as used in the Barraquer technique.
To this end, the invention provides a surgical instrument for performing lamellar cutting of the cornea and comprising:
a ring-shaped base shaped for being applied to and held against the eye; and
a cutting tool having a cutting blade received in a support co-operating with the base to guide displacement of the cutting edge of the blade in a plane parallel to the ring, and including, in front of the blade, a shaping element for shaping the portion of the cornea that projects into the ring, wherein the shaping element is constituted by a roller coupled to the blade support about an axis of rotation perpendicular to the cutting direction.
Thus, unlike existing instruments, the cornea is no longer shaped by a plate which compresses it, but by a member which rolls on the cornea without sliding, thus making it possible firstly to obtain resection of thickness that is uniform or non-uniform in the transverse direction, and secondly to vary the thickness of the resection as cutting advances. Thus a flattening plate makes it possible to perform resection that is parallel only to the anterior surface of the cornea, whereas the roller of the invention makes it possible to perform resection of varying profile, and in particular of profile that is parallel to the posterior surface of the cornea which is known to be thicker at the periphery than in the center. This makes it possible in a single resection operation to modify the curvature of the cornea in order to correct ametropia, once it has been determined what shape needs to be given to the outside surface of the cornea, and thus what profile it is to have after correction. It is also possible with the instrument of the invention to combine mechanical resection of a corneal flap of determined profile and then to add additional resection of a lenticule or some other portion of the stroma before folding down the flap.
Thus, in the instrument of the invention, the roller can be either cylindrical, or barrel-shaped, or diabolo-shaped. It can also be given any other useful shape, and in particular it can be cylindrical and possess a lens applied in relief on its outside surface. In the same manner, it can be cylindrical and possesses a lens-shaped depression in its outside surface. When its outside surface is not a surface of revolution, the roller should have an index associated with the position of a particular generator line on its peripheral surface and the support should include a mark for locating the index in a determined position, in particular at the beginning of an operation.
Advantageously, the peripheral surface of the shaper member is provided with microrelief to enhance rolling without slip on the surface of the cornea.
Furthermore, and in particular for large-diameter cuts, it can be advantageous to place a plate in front of the roller so as to avoid pressure variations in the eye. The distance between the blade and the rear edge of the plate can be about 5 millimeters (mm) to 6 mm.
Finally, and also advantageously, the annular base has a groove in its face directed towards the eye, the groove being partitioned by an intermediate wall provided with at least one opening providing communication between the two portions of the groove.